1. Field of the Invention
The present invention relates to an electronic component such as a lamination-type piezoelectric resonator component, having a structure in which an element substrate having an electronic component element disposed thereon is laminated to a sealing substrate via an adhesive layer, and to a method of producing such an electronic component.
2. Description of the Related Art
Heretofore, various types of lamination-type piezoelectric resonator components, in each of which element substrates are bonded to the upper and lower surfaces of an energy-trap type piezoelectric resonator element through adhesives, have been proposed. For example, Japanese Unexamined Patent Application Publication No. 8-23253 discloses a piezoelectric resonator component in which sealing substrates are bonded to an element substrate having at least two energy trap type piezoelectric resonating portions mounted on both main surfaces thereof via adhesives, respectively.
An example of the configuration of this type of related art piezoelectric resonator component will be described with reference to FIG. 8.
In a piezoelectric resonator component 101, sealing substrates 105 and 106 are bonded to the upper and lower surfaces of an element substrate 102 through adhesive layers 103 and 104. First and second energy trap type piezoelectric resonating portions 107 and 108 are disposed on the element substrate 102. The piezoelectric resonating portions 107 and 108 contain vibration electrodes 107a, 107b, 108a, and 108b which are disposed on both the main surfaces of the element substrate 102, respectively.
The vibration electrodes 107a and 108a are connected to terminal electrodes 109 and 110 in the portions of the component not shown in FIG. 8. Moreover, the vibration electrodes 107a and 108a are also connected to a capacitor electrode 111. On the other hand, the vibration electrodes 107b and 108b are electrically connected to a capacitor electrode 112 on the lower surface of the element substrate 102.
Thus, a capacitor-containing piezoelectric oscillator having the two piezoelectric resonating portions and one capacitor is provided.
The sealing substrates 105 and 106 are bonded through the adhesive layers 103 and 104 so as to define spaces which prevent disturbance of the vibration of the piezoelectric resonating portions 107 and 108. Moreover, end surface electrodes 113 and 114 are disposed on the end surfaces of the laminate including the element substrate 102 and the sealing substrates 103 and 104, respectively. The end surface electrodes 113 and 114 are electrically connected to the terminal electrodes 109 and 110.
External electrodes 115 to 118 are disposed on the upper and lower surfaces of the laminate. The external electrodes 115 and 116 are electrically connected to the end surface electrode 113. The external electrodes 117 and 118 are electrically connected to the end surface electrode 114.
Also, an external electrode 121 is disposed in the center of the laminate so as to wind around the upper surface, a pair of the side surfaces, and the lower surface of the laminate. The external electrode 121 is electrically connected to the capacitor electrode 112.
Referring to the production of the piezoelectric resonator component 101, a mother laminate is prepared for improving productivity. The mother laminate is cut in the thickness direction, so that laminates as individual units of the piezoelectric resonator component 101 excluding the end surface electrodes 113 and 114 are produced. Thereafter, a pair of the end surfaces of the laminate onto which the terminal electrodes 109 and 110 are exposed are surface-roughened by sand-blasting or barrel polishing. The surface-roughening is carried out in order to securely expose the end surfaces of the terminal electrodes 109 and 110 and also to improve the bond strength of the end surface electrodes. Thereafter, the end surface electrodes 113 and 114 are formed by a thin-film forming technique such as vapor-deposition, sputtering, or the like.
As described above, prior to the formation of the end surface electrodes 113 and 114 in the production of the piezoelectric resonator component 101, the surface-roughening for exposure of the end surfaces of the terminal electrodes 119 and 110 is carried out. In this case, the adhesive layers 103 and 104 are also scraped off by the polishing. The adhesive layers 103 and 104 are formed from an epoxy adhesive having a high bond strength. The epoxy adhesive having a superior bond strength presents a high stiffness when the adhesive is completely cured. Therefore, when the sand-blasting or the barrel-polishing is carried out, the adhesive layers 103 and 104 are scraped off as shown in FIG. 9 and readily recede from the end surface of the laminate toward the inside thereof. That is, the outside ends 103a and 104a of the adhesive layers 103 and 104 readily recede inward of the laminate from the end surface thereof. In the case where the receding amount is large, the end surface electrode 113, which is formed by vapor deposition or sputtering, may be broken and separated as shown in FIG. 9. In particular, for the end surface electrode 113 formed by a thin-film forming technique such as vapor deposition and sputtering, the film is relatively thin. On the other hand, the adhesive layers 113 and 114 have thicknesses such that they can define spaces which prevent disturbance of the vibration in the thickness direction of the piezoelectric resonating portions 107 and 108.
Accordingly, when the outside ends 103a and 104a of the adhesive layers 103 and 104 recede, the end surface electrode 113 may be broken and separated at the outside ends 103a and 104a of the adhesive layers 103 and 104, so that the electrical connection of the terminal electrode 109 to the outside electrodes 115 and 116 can not be achieved. Moreover, even if the electrical connection is achieved, the reliability of the electrical connection between the end surface electrode portions disposed on the element substrate 102 and the end surface electrode portions disposed on the sealing substrates 103 and 104 may be insufficient.